﻿Shader "UI/ImageOutline" {
	Properties{
			_MainTex("Sprite Texture",2D) = "white"{ }
			_Color("Tint",Color) = (1,1,1,1)

			_StencilComp("Stencil Comparison",Float) = 8
			_Stencil("Stencil ID",Float) = 0
			_StencilOp("Stencil Operation",Float) = 0

			_StencilWriteMask("Stencil Write Mask",Float) = 255
			_StencilReadMask("Stencil Read Mask",Float) = 255

			_ColorMask("Color Mask",Float) = 15

			[Toggle(UNITY_UI_ALPHACLIP)] _UseUIAlphaClip("Use Alpha Clip",Float) = 0

			_OutlineColor("My Outline Color",Color) = (1,1,1,1)
			_OutlineWidth("My Outline Width",Float) = 2
			_Threshold("My Threshold",Range(0,1)) = 0.5
	}
		SubShader{
			Tags
				{
					"Queue" = "Transparent"
					"IgnoreProjector" = "True"
					"RenderType" = "Transparent"
					"PreviewType" = "Plane"
					"CanUseSpriteAtlas" = "True"
				}

				Stencil
				{
					Ref[_Stencil]
					Comp[_StencilComp]
					Pass[_StencilOp]
					ReadMask[_StencilReadMask]
					WriteMask[_StencilWriteMask]
				}

				Cull Off
				Lighting Off
				ZWrite Off
				ZTest[unity_GUIZTestMode]
				Blend SrcAlpha OneMinusSrcAlpha
				ColorMask[_ColorMask]

				Pass
				{
					CGPROGRAM
#pragma vertex vert 
#pragma fragment frag

#include "UnityCG.cginc"
#include "UnityUI.cginc"

#pragma multi_compile __ UNITY_UI_ALPHACLIP

				struct appdata_t
				{
					float4 vertex : POSITION;
					float4 color :COLOR;
					float2 texcoord:TEXCOORD0;
				};

				struct v2f
				{
					float4 vertex : SV_POSITION;
					fixed4 color : COLOR;
					half2 texcoord : TEXCOORD0;
					float4 worldPosition : TEXCOORD1;
				};

				fixed4 _Color;
				fixed4 _TextureSampleAdd;
				float4 _ClipRect;

				v2f vert(appdata_t IN)
				{
					v2f OUT;
					OUT.worldPosition = IN.vertex;
					OUT.vertex = UnityObjectToClipPos(OUT.worldPosition);

					OUT.texcoord = IN.texcoord;

#ifdef UNITY_HALF_TEXEL_OFFSET
					OUT.vertex.xy += (_ScreenParams.zw - 1.0)*float2(-1, 1);
#endif

					OUT.color = IN.color * _Color;
					return OUT;
				}
				sampler2D _MainTex;
				float4 _MainTex_TexelSize;

				float4 _OutlineColor;
				float _OutlineWidth;
				float _Threshold;

				fixed4 frag(v2f IN) : SV_Target
				{
					half4 color = (tex2D(_MainTex,IN.texcoord) + _TextureSampleAdd) * IN.color;
					color.a *= UnityGet2DClipping(IN.worldPosition.xy, _ClipRect);

#ifdef UNITY_UI_ALPHACLIP
					clip(color.a - 0.001);
#endif
					float width = _MainTex_TexelSize.z, height = _MainTex_TexelSize.w;

					if (color.a <= _Threshold)
					{
						half2 dir[8] = { {0,1},{1,1},{1,0},{1,-1},{0,-1},{-1,-1},{-1,0},{-1,1} };
						for (int i = 0; i < 8; i++)
						{
							float offset = float2(dir[i].x / width, dir[i].y / height);
							offset *= _OutlineWidth;

							half4 nearby = (tex2D(_MainTex, IN.texcoord + offset) + _TextureSampleAdd) * IN.color;
							if (nearby.a > _Threshold)
							{
								color = _OutlineColor;
								break;
							}
						}
					}
					return color;
				}
					ENDCG
				}
			}
}
